It seems somewhat similar to weight classes in wrestling, actually. I wonder if there's a way to do that in other sports.... Sorting runners by how fast they are doesn't *quite* make sense though.

There's really no reason to do that for running. I don't think there's anyone that cares who is the fastest per height/weight/whatever combination of criteria you want. Whereas for wrestling/boxing/weightlifting your ability to compete is very much proportional to your weight. And you can display technical skill in any weight bracket, whereas for running...you really just want to be as fast as possible.

That is true about wrestling... What if runners were sorted into groups based on leg length? I wonder what the results would look like.

I think the correlation between leg length and speed is complicated and low compared to the correlation between weight and boxing/wrestling/lifting skill.

The idea is that you can show technical proficiency and skill at different weight classes and that people care about such things. Showing "technical proficiency" in running is just way less important than absolute speed.